Boiler tube wearbar, stud welder and arc shield

Abstract

Apparatus and methods for replacing or repairing missing or damaged abrasion resistant wearbars utilized in high velocity cyclone boilers. A retrofit wearbar having an aperture therein is utilized in conjunction with an end weldable stud wherein the wearbar and stud are placed in position over a damaged wearbar or against the boiler tube in the case of a missing wearbar and the stud end welding technique utilized to fuse the wearbar and stud in place with the damaged wearbar or boiler tube in the case of a missing wearbar in situ. An arc shield is utilized which has a projection from the weld fillet cavity thereof which cooperates in conjunction with the aperture of the retrofit wearbar to provide alignment of the stud in the wearbar and prevent shorting of the stud to the wearbar during the welding cycle.

What is claimed is: 
     
       1. In stud welding apparatus employing a stud welding gun, a stud carried by the stud welding gun and an arc shield surrounding the stud wherein the arc shield is carried by the stud welding gun at one end and terminates at its opposite end in an arc shield body, the improvement in the arc shield permitting welding of the stud through an aperture of a given configuration in a first workpiece comprising: a projection extending from the arc shield body of configuration complementary with the aperture to align the stud in respect to the aperture to prevent shorting of the stud with the aperture of the first workpiece. 
     
     
       2. The improvements of claim 1 wherein the arc shield includes a weld fillet cavity formed in the arc shield body and vent slots through the projection and arc shield body as to permit escape of gases generated during the welding of the stud. 
     
     
       3. The improvements of claim 1 or claim 2 wherein the projection is frusto-conical. 
     
     
       4. The improvements of claim 3 wherein the projection terminates at its upper extremity in a shoulder which is adapted to engage the upper extremity of the aperture. 
     
     
       5. The improvements of claim 4 wherein the frusto-conical projection at its major diameter approximates the size of the aperture.